In crop protection, it is principally desirable in principle to increase the specificity and the reliability of the action of active compounds. In particular, it is desirable for the crop protection product to control the harmful plants effectively and, at the same time, to be tolerated by the useful plants in question.
Naptalam, i.e. N-1-naphthylphthalamic acid [IUPAC], sometimes also termed as NPA or Alanap™, its salts and esters such as naptalam-sodium are well known herbicide active compounds (see C. D. S Tomlin (Ed.), The Pesticide Manual, 14th ed., 2006, BCPC Alton, Hampshire, UK, pp. 746 f.). Naptalam is known to possess herbicidal action against broadleaf weeds and some grasses.
Historically, naptalam was used as a preemergence and postemergence herbicide alone or in combination with other herbicides at application rates of 2000 to 5500 g/ha (see “The Pesticide Manual” loc. cit). However, the herbicidal activity and the activity spectrum are limited and the required application rates are high by contemporary standards.
GB 1,063,234 suggests a combined application of naptalam or its salts with phenoxyaliphatic carboxylic acid herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D), (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2-(2-methyl-4-chlorophenoxy)propionic acid (mecoprop), 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) or salts thereof. The activity spectra of the mixtures are shown to be broader than the activity spectrum of the individual compounds.
A formulation containing naptalam and 2,4-DB was commercially available under the tradename Rescue® from Chemtura. The formulation had been suggested for controlling broadleaf weeds in crops of soybean.
Furthermore, it has been suggested to co-apply naptalam with one of the following herbicides: clomazone, halosulfuron-methyl, bensulide, chlorothal, trifluralin, ethalfluralin or clomazone plus ethalfluralin.
From EP 646315 it is known that the herbicidal activity of certain herbicides can be increased by the combined application with certain herbicidal semicarbazones, such as diflufenzopyr, which belongs to the group of auxin transport inhibitors (group P of the HRAC classification system: HRAC, Classification of Herbicides According to Mode of Action, http://www.plantprotection.org/hrac/MOA.html). Unfortunately, the combined application of these herbicidal semicarbazones with certain other herbicides in certain crops such as cereals, cotton, soybean or turf leads to damage of the crop plants.